Just joining you all thanks to a suggestion by John of RadioBoatAnchor

Some years ago my son and I were given a Graymark 508 classroom project (see attached), and I've been sitting on it until now - that my 11 y.o. son is old enough to be interested.

Unpacking it, we discovered that it didn't include even a simple schematic. No problem, I thought ... surely we'll find something on the web. Testing my over-inflated sense of google-searching prowess, I haven't been able to find one - outside of an eBay'er selling a whole kit with unspecified documentation, and clearly stating in the ad that the literature would not be shared.

Looking at the board in the kit, it's pretty well labeled. Almost feels like we could figure it out - but that again is how my overconfidence and ignorance has treated me to frequent popped caps and smoked resistors.

So my questions to the community are:

"Any chance that idea could hold any water? Could that puzzle be solved without schematics?"

We moved to Ireland a few months ago, so the time change thing has gotten in the way of timely correspondence with people in the states.

Hopefully, I'll have those caps in my drawers, if not, I'll have to begin to find where best to order components from over here.

We'll post updates, and look forward to more conversations with this community.

P.S. I'm a big fan of old-time radio and radio drama. When I was a kid, I listened a lot to CBS Radio Mystery Theater on the very radio in my avatar. Good old Archer Road Patrol that I took from my bike handlebars to bed with me at night. I love AM radio, and played around with box loop antennas when I was a kid to bring-in the distant stations.

But still have four Ray-O-Vac "D" batteries that came in a multi-band radio given me in 1974 that still were perfectly good a couple years ago (need to check 'em again)---the radio was given away long ago, but kept them ! Weren't used much, but held their power...

Ok, well ... we finally had a minute to breadboard the kit and are coming back to you all for assistance.

Not sure where to continue troubleshooting. We've gone over the diagram several times to check our connections and directions of components; verified power at the rails; pulled no current readings across either transistor's leads.

Should we start checking and replacing individual components? Start with the transistors?

Apologies for the messy board. The layout has some quirks with lots of jumpers used to get space for connections. (T3's physical layout has diagonal connections)

Use a VOM and check transistors for leakage, consider replacement. Replace the electrolytics if they are OEM.

Circuit is a reflex. May have to swap one winding of the RF transformer either to make it work or to stop oscillation. That may be what is happening, locked up oscillating. Or, how is Q2 getting its collector volts?

Best check some of the online schematics...

No excuses for the pin-board rats nest. Even at 10 mhz a pin board will be fine with rails laid our properly. It's common practice to stand the resistors up. A hairpin loop of #22 bus sufficed to make a soldered wire connection rather than depend on a tinned stranded wire into a rail. When complete, blobs of hot melt will hold things solid. I OFTEN had arrange and re-arrange a breadboard circuit to get both a neat, compact workable circuit. I have never had a circuit of which had issues with coupling between the rails.

I did my patent models on pin board, there were shipped to test facilities all over the country and GB. worked fine...

Thank you all for the tips, and esp. to Rocco for the time spent on the diagram update! We had wondered about the extra cap. LOL ... Kinda felt like the handful of extra nuts and bolts left after working on the car

Interestingly, drawing then re-drawing the schematic, that is as long as the drawing remains correct. It will become obvious what each and every component is doing.

A boys radio is not unlike the 20's era reflex radios, each and every component is vital.

Yet consider when they were designed and made, late 50's I recall bicycling 6 miles to a large department store to buy my first radio a Boys two transistor radio that worked so great withing viewing distance of the radio towers. Back home I could barely hear one station.Then, the radio was $2.95, other stores had similar radios from $4.95 to $9.95.

Considering the store is marking up 40%, the distributor another 10%, factory profiting another 50 to 90% its easy to see the radio probably cost less than 50 cents to make.

And we wonder about the quality of the parts, no question bottom of the barrel...

Rocco53, exchange the start/finish of one winding on the coupling transformer T3 only. Turning around the transformer will exchange the ratio but not the "polarity" If this is a radio on a circuit board then turning it around is the only option unless the terminals or board are labeled such that the transformer fits but one way. The drawing seems to indicate a step-up from the transistor to the detector diode as well as marker dots for the primary winding.